An air-conditioning and ventilation apparatus has a total heat exchanger incorporated therein that performs heat exchange between supply air and exhaust air, and it also includes an air-conditioning coil incorporated therein intended for heating and cooling and that is located immediately behind the total heat exchanger in an air trunk on the supply air side. The air-conditioning and ventilation apparatus performs heat exchange between supply air and exhaust air with the total heat exchanger. The heat-exchanged supply air is heated or cooled by the air-conditioning coil, the indoor air and outdoor air being exchanged simultaneously with air supply and exhaust, so as to be humidified or dehumidified.
In a humidity control and ventilation apparatus disclosed in Patent Literature 1, heat exchange is performed between supply air supplied from outside into the room and exhaust air exhausted from the room to outdoors. When the outdoor temperature is equal to or higher than the preset reference temperature, control is executed to perform a dehumidifying function, and when the outdoor temperature is lower than the preset reference temperature, control is executed to perform a humidifying function.
A ventilation apparatus disclosed in Patent Literature 2 includes a control unit that controls a heating amount of an air-conditioning coil depending on outdoor air temperature and humidity so that absolute humidity of supplied air, which is from an air-conditioning and ventilation apparatus into the room, becomes equal to or higher than a reference value in order to satisfy a required humidifying amount in which a safety factor is added to an absolute humidity difference between indoor air and outdoor air with respect to indoor absolute humidity obtained on the basis of preset indoor temperature and indoor humidity.
In the dehumidification control of a heat exchange and ventilation apparatus, a known technique is to execute control to perform a dehumidifying function when the capacity of an air-conditioning coil is 100% or a fixed value lower than 100%, all times irrespective of outdoor humidity when the outdoor temperature is in a range in which a dehumidifying operation can be performed. Also a known technique is to execute control to obtain air temperature after heat exchange by calculation on the basis of target temperature set beforehand by a remote controller and detection results of indoor temperature and outdoor temperature, and to perform a dehumidifying function so that the capacity of an air-conditioning coil changes on the basis of only a temperature difference between the calculated value and the target temperature. In these techniques, the dehumidifying operation is continued irrespective of the outdoor humidity. Accordingly, there has been a problem that, even if a dehumidification load due to an absolute humidity difference between indoor air and outdoor air is small, blown-out temperature of the ventilation and air-conditioning apparatus drops excessively, thereby causing dew condensation on a surface of a blow-out grill.
As an example of executing temperature and humidity control locally in a room, an air-conditioning apparatus disclosed in Patent Literature 3 includes a control unit that sets target temperature and target humidity to control an indoor fan, a cooling dehumidifier, and a reheater on the basis of the set target temperature and target humidity, thereby enabling to control temperature and humidity in an area to be air-conditioned.
Furthermore, an air conditioner disclosed in Patent Literature 4 determines an operation mode on the basis of detected indoor temperature and outdoor air temperature during the dehumidifying operation; controls a compressor by providing a correction amount to the compressor rotation number depending on a difference between indoor humidity and indoor set humidity; and also controls an outdoor fan by providing a correction amount to the outdoor fan rotation number depending on a difference between detected room temperature and set temperature, thus performing correction of the compressor and correction of the outdoor fan alternately at a predetermined time interval and thereby executing stable control around the set temperature and humidity.
In the dehumidification control of an air conditioner that can perform reheating and dehumidification disclosed in Patent Literature 5, a difference ΔX between humidity or absolute humidity in an air-conditioned room and target humidity or absolute humidity is calculated; target evaporation temperature is set on the basis of the difference ΔX so as to execute the dehumidification control of controlling the rotation number of a compressor on the basis of the target evaporation temperature; and a difference ΔTr between detected temperature of the air-conditioned room and target temperature is simultaneously calculated to execute temperature control of controlling an opening degree of an expansion valve of an indoor coil on the basis of the difference ΔTr.